Rotary compressors for compressing fluid known in the art have been widely applied for apparatuses such as refrigerating apparatuses.
For example, a rotary compressor disclosed in Japanese Unexamined Patent Publication No. 2007-154657 has a casing including an electric motor and a compression mechanism. The electric motor includes a stator fixed to the casing, and a rotor inserted into the stator. The compression mechanism is connected to the electric motor via the drive shaft. The compression mechanism includes a cylinder having a cylinder chamber, and a piston fitted onto an eccentric portion of the drive shaft. When the electric motor receives power, the rotor rotates inside the stator. Accordingly, the drive shaft and thus the piston rotate. The rotation of the piston reduces the volume of the cylinder chamber to compress the fluid in the chamber.
The rotary compressor cited in Japanese Unexamined Patent Publication No. 2007-154657 includes a balance weight mechanism to obtain a proper mass balance between the balance weight mechanism and the eccentric part of the drive shaft. Specifically, the balance weight mechanism, which is shaped into an approximate column, includes a solid portion and a hollow portion to adjust the mass balance. Furthermore, an outer end portion of the balance weight mechanism has a flat portion in the axial direction. The balance weight mechanism is fixed to the rotor by a rivet inserted into the flat portion.
Hence, the balance weight mechanism fixed to the rotor enables the rotary compressor cited in Japanese Unexamined Patent Publication No. 2007-154657 to obtain a proper mass balance between the balance weight mechanism and the eccentric part to reduce vibration of the rotary compressor. Furthermore, the flat portion provided to the balance weight mechanism reduces agitation loss caused by the rotation of the balance weight mechanism.